add: leetcode - 460 lfu cache

Leetcode/460-lfu-cache/KwonYG/index.js

@@ -0,0 +1,137 @@
+class Node {
+  constructor(key, value) {
+    this.key = key
+    this.val = value
+    this.next = this.prev = null
+    this.freq = 1
+  }
+}
+
+class DoublyLinkedList {
+  constructor() {
+    this.head = new Node(null, null)
+    this.tail = new Node(null, null)
+    this.head.next = this.tail
+    this.tail.prev = this.head
+  }
+
+  insertHead(node) {
+    node.prev = this.head
+    node.next = this.head.next
+    this.head.next.prev = node
+    this.head.next = node
+  }
+
+  removeNode(node) {
+    let prev = node.prev
+    let next = node.next
+    prev.next = next
+    next.prev = prev
+  }
+
+  removeTail() {
+    let node = this.tail.prev
+    this.removeNode(node)
+    return node.key
+  }
+
+  isEmpty() {
+    return this.head.next.val == null
+  }
+}
+
+/**
+ * @param {number} capacity
+ */
+const LFUCache = function (capacity) {
+  this.capacity = capacity
+  this.currentSize = 0
+  this.leastFreq = 0
+  this.nodes = {} // 순서에 상관없이 노드들이 저장되는 공간
+  this.freqs = {} // 참조횟수를 키값으로 가지는 이중 연결 리스트 저장 공간
+}
+
+/**
+ * @param {number} key
+ * @return {number}
+ */
+LFUCache.prototype.get = function (key) {
+  let node = this.nodes[key]
+  if (!node) {
+    return -1
+  }
+
+  this.freqs[node.freq].removeNode(node)
+
+  // 다음에 어떤 항목을 제거할 지 결정한다.
+  if (node.freq == this.leastFreq && this.freqs[node.freq].isEmpty()) {
+    this.leastFreq++
+  }
+
+  node.freq++
+  if (this.freqs[node.freq] == null) {
+    this.freqs[node.freq] = new DoublyLinkedList()
+  }
+
+  this.freqs[node.freq].insertHead(node)
+
+  return node.val
+}
+
+/**
+ * @param {number} key
+ * @param {number} value
+ * @return {void}
+ */
+LFUCache.prototype.put = function (key, value) {
+  if (this.capacity == 0) {
+    return
+  }
+  let node = this.nodes[key]
+
+  if (!node) {
+    this.currentSize++
+    if (this.currentSize > this.capacity) {
+      let tailKey = this.freqs[this.leastFreq].removeTail()
+      delete this.nodes[tailKey]
+      this.currentSize--
+    }
+    let newNode = new Node(key, value)
+
+    if (this.freqs[1] == null) {
+      this.freqs[1] = new DoublyLinkedList()
+    }
+    this.freqs[1].insertHead(newNode)
+
+    this.nodes[key] = newNode
+    this.leastFreq = 1
+  } else {
+    node.val = value
+    this.freqs[node.freq].removeNode(node)
+
+    if (node.freq == this.leastFreq && this.freqs[node.freq].isEmpty()) {
+      this.leastFreq++
+    }
+
+    node.freq++
+
+    if (this.freqs[node.freq] == null) {
+      this.freqs[node.freq] = new DoublyLinkedList()
+    }
+
+    this.freqs[node.freq].insertHead(node)
+  }
+}
+
+const cache = new LFUCache(5 /* capacity */)
+
+console.log(cache.put(1, 1)) // freqs 상태: {1: 1}
+console.log(cache.put(2, 2)) // freqs 상태: {1: 2 <-> 1}
+console.log(cache.put(3, 3)) // freqs 상태: {1: 3 <-> 2 <-> 1}
+console.log(cache.put(4, 4)) // freqs 상태: {1: 4 <-> 3 <-> 2 <-> 1}
+console.log(cache.put(5, 5)) // freqs 상태: {1:  5 <-> 4 <-> 3 <-> 2 <-> 1}
+console.log(cache.get(1)) // 1 반환  freqs 상태: {1:  5 <-> 4 <-> 3 <-> 2,  2: 1}
+console.log(cache.get(1)) // 1 반환  freqs 상태: {1:  5 <-> 4 <-> 3 <-> 2,  3: 1}
+console.log(cache.get(1)) // 1 반환  freqs 상태: {1:  5 <-> 4 <-> 3 <-> 2,  4: 1}
+console.log(cache.put(6, 6)) // freqs 상태: {1:  6 <-> 5 <-> 4 <-> 3,   4: 1}
+console.log(cache.get(6)) // 1 반환  freqs 상태: {1:  5 <-> 4 <-> 3 <-> 2,  4: 1  2:6}